Field of the Invention
The present invention relates to a nozzle plate of a hydraulic engine mount in which a hydraulic liquid is encapsulated and flows between an upper liquid chamber and a lower liquid chamber through a flow path formed in the nozzle plate, and more particularly, to a nozzle plate of an engine mount, which is capable of suppressing rattling noise of a membrane that is mounted on the nozzle plate and vibrates when a hydraulic liquid flows.
Description of Related Art
A hydraulic engine mount is configured to attenuate vibration in a high frequency region and a low frequency region, and widely used for various types of vehicles.
FIG. 1 illustrates a state of an interior of a hydraulic engine mount (hereinafter, referred to as “engine mount”) in the related art. Referring to FIG. 1, the engine mount has an internal space provided between an insulator 2 and a diaphragm 3, the predetermined amount of hydraulic liquid is encapsulated in the internal space, and the internal space is divided into an upper liquid chamber and a lower liquid chamber by a nozzle plate 4 mounted in the internal space.
The nozzle plate 4 is configured by coupling an upper nozzle plate 5, a lower nozzle plate 7, and a membrane 6, and a flow path is formed in the upper nozzle plate 5 and the lower nozzle plate 7 so that the hydraulic liquid may flow through the flow path.
That is, a circular flow path groove is formed in an upper surface of the lower nozzle plate 7, and the upper nozzle plate 5 is coupled onto the lower nozzle plate 7 so as to cover an upper side of the flow path groove, thereby forming the flow path. Further, a lower entrance hole and an upper entrance hole, which communicate with the flow path groove, are formed in the lower nozzle plate 7 and the upper nozzle plate 5, respectively, at both side ends of the flow path groove. Therefore, the flow path communicates with the lower liquid chamber through the lower entrance hole, and communicates with the upper liquid chamber through the upper entrance hole.
The membrane 6, which vibrates when the hydraulic liquid flows, is selectively mounted between the upper nozzle plate 5 and the lower nozzle plate 7. The membrane 6 is mounted such that a rim portion thereof is engaged between the upper nozzle plate 5 and the lower nozzle plate 7, and each of the upper nozzle plate 5 and the lower nozzle plate 7 has a shape having an opening hole so that the hydraulic liquid in the upper liquid chamber and the lower liquid chamber is in contact with the membrane.
With a change in load of an engine which is transmitted through a core 1, the insulator 2 is elastically deformed, and thus a volume of the upper liquid chamber is changed, and as a result, the hydraulic liquid flows between the upper liquid chamber and the lower liquid chamber through the flow path. In this case, in addition to the flow path, when the membrane vibrates, the hydraulic liquid flows through a gap formed at a portion where the membrane is engaged.
That is, in a situation in which large displacement behavior is inputted such as when a vehicle suddenly accelerates or travels on a rough road, the hydraulic liquid flows through the flow path so as to generate a relatively high damping value, and in a situation in which small displacement vibration is inputted such as when the vehicle travels on a normal road or an engine idles, the hydraulic liquid flows through the gap and the membrane vibrates, thereby generating a damping value.
However, in the case of a structure in the related art, there is a problem in that the rim portion of the membrane strikes the upper nozzle plate 5 and the lower nozzle plate 7 when the membrane vibrates, and as a result, abnormal noise occurs. To inhibit the occurrence of the abnormal noise, a method of reducing a clearance by increasing a thickness of a portion where the membrane 6 is engaged (semifixed membrane), or a method of completely fixing the membrane so that no clearance is formed (integrated membrane) is used in the related art.
However, there are problems in that if the thickness of the portion where the membrane is engaged is increased, a magnitude of abnormal noise is reduced, but dynamic characteristics are increased, and as a result, NVH (noise, vibration, harshness) performance deteriorates, and the structure in which the rim portion of the membrane 6 is fixed to the nozzle plate 4 degrades damping efficiency.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.